(597f) Simulation and Comparative Evaluation of Different Methods of Microalgal Lipid Extraction and Conversion to Biodiesel Using Aspen HYSYS

Microalgal lipids are prized commodity for its tremendous potential to be used directly as a bio-diesel equivalent. Microalgal derived biofuels can be used as it is in modern day transportation vehicles, without much engine modification. Foreseeing the trend of mindless use of exhaustible fossil fuel reserves, increased demand and insufficient supply sources, it is imperative to devise efficient systems of bio-diesel production. Microalgae is one such green and relatively cost-effective option for biodiesel production. Biodiesel is essentially similar to diesel but with some biological characteristics. Better processing of biodiesel could give same value as that of diesel with less environmental damage, thus it should be explored as a viable alternative. However, the major bottleneck associated with production of biodiesel from microalgae at commercial scale lies in high costs associated with various unit operations of the microalgal bio-oil production such as cultivation, harvesting and downstream cost mainly in product recovery steps. There are several methods which have been used for the lipid extraction from microalgal biomss like: bead beating, homogenizing, sonication, solvent extraction, supercritical fluid extraction etc or simultaneous extraction and transesterification process for the conversion of microalgal lipids into fatty acid methyl esters or FAME (bio-diesel).
Generally, lipids are triglycerides which react with alcohol to produce ester by transesterification reaction in the presence of acid/base catalyst. Every method involves use of different types of solvent, physical condition (eg. temperature, pH etc) electricity consumption (cell disruption). The paper presents an overall overview of process modeling of different methods of lipid extraction from the microalgal biomass and its conversion into biodiesel using Aspen Plus software. Using Aspen, each unit operation, and flow stream, physical properties of each reactant, product and intermediate is run sequentially until convergence and careful mass and energy balance is designed. Every aspect of the process is taken into account such as cell disruption, extraction, transesterification etc and the final biodiesel yields compared from different processes. Additional, other properties such as cloud point, cetane number and heating value of the algae biodiesel was assessed and compared. The possibility of any by-product generation such as glycerol was considered.
The above discussed comparisons of technologies and processing conditions allow to select the best options, for each process stage from an environmental perspective. After the oil extraction and conversion, the economy results is dependent on the final use (and quality) of the microalgae oil free cake. It could be used as a substrate for biogas production or as animal feed, fertilizer etc. It was observed through Aspen modeling that rather than individual processes of oil extraction and conversion, simultaneous extraction and transesterification significantly affects overall performance of the process. The simulation results demonstrate promising results in terms of product recovery, yield, and product quality and could be used to select best choice for microalgal biodiesel production.